Technical Abstract:
Soil compaction is a concern in crop production and environmental protection. Compaction is most often quantified in the field, albeit indirectly, using cone penetrometer measurements of soil strength, reported as cone index (CI). In this research, CI data collected under different soil conditions (e.g., texture and water content) were analyzed to detect variations in soil compaction and to define parameters useful for compaction management (e.g., location of and depth to compacted zones). CI profiles were collected on a 20- to 30-m grid spacing from two fields with variations in soil texture, bulk density, and water content. Auxiliary data collected were bulk density, water content, and apparent soil electrical conductivity (ECa) as a surrogate for soil texture. Results indicated that the effects of ECa, bulk density, and soil water content on CI were different for different sites, depths, and ECa ranges (or clay content). Maps of CI showed spatial and vertical variability, indicating that the locations of and depths to layers restricting crop growth were not uniform over entire fields. When 2 MPa was used as a threshold CI value to delineate compacted areas, the portion of each field needing management to reduce compaction was 21% and 36%. This indicated that site-specific and depth-specific field management (e.g., tillage) could be more efficient in terms of energy and labor than conventional uniform field management.